Integration of facies and reservoir analyses presents three main difficulties: (1) the volume of data is huge; (2) few causal relations between petrographic and reservoir properties are known; and (3) geologic data range from quantitative to purely qualitative.

Multivariate statistical methods offer a fruitful approach to the problem. A mathematically derived index allows determination of the similarity between two rock samples by simultaneously considering many environmentally significant variables which may be measured on different scales. A factor analysis of those similar coefficients portrays groups of rock samples that are environmentally distinct (environmental facies).

This same procedure can be used to determine reservoir facies (groups of rock samples with similar reservoir properties). Also, the reservoir properties in each of the environmental facies can be characterized and tested for distinctness. These environmental and reservoir facies must be established before relations between rock properties and reservoir properties can be established. These can be effectively determined by multiple regression and canonical correlation.

This approach was applied to the Redwater field; part of an Upper Devonian reef complex and nine environmental facies were outlined. This gave a detailed picture of reef zonation, from which the mechanics of reef growth could be interpreted. Analysis of the reservoir properties within these facies showed only four reservoir facies.

The study showed that the reservoir properties are controlled primarily by variables sensitive to the original environment of deposition. Porosity-permeability variation also is controlled by properties which reflect the amount and type of diagenesis. Diagenesis, in turn, is shown to be related to original environment.

End_of_Article - Last_Page 621------------